This core unit serves as a central resource for normal and hypertensive animals used by all investigators in the Program Project. Core personnel are responsible for continuing and up-to-date assessment of animal requirements for all Projects. They ensure timely ordering, delivery, and proper housing of animals. All animal surgery (except some post-mortem tissue removal) is conducted and/or supervised by Core B personnel. This includes production of DOCA-salt and S6c-induced hypertension and appropriate control or sham-operated rats, most routine tissue removal for in vitro analysis, and instrumentation of rats for chronic hemodynamic monitoring. All animals used in the Program Project have their blood pressure carefully and reliably quantified by Core B personnel either directly (implanted arterial catheter or radiotelemetry transmitter) or indirectly (systolic pressure by tail-cuff sphygmomanometry) prior to or as part of each experimental protocol. Daily animal husbandry, health surveillance and record keeping also are the responsibility of Core B personnel, in association with the staff of University Laboratory Animals Resources (ULAR) of Michigan State University. Core B personnel also are responsible for developing and implementing new physiological techniques for evaluating cardiovascular function in rats. A major advantage of the Animal Core is that it facilitates the most efficient use of animals by Program Investigators. It is our usual practice to schedule tissue sample collection from an individual rat in such as way as to allow at least two, and often three or more, investigators to obtain needed tissues from the same animal. Our in vivo protocols also are designed to maximize the amount of data collected from a single animal. This is achieved through use of long-term repeated measurements of cardiovascular parameters, rather than studying separate groups of rats at each time point of interest. Often at the end of chronic in vivo protocols, tissue samples from the rats are distributed to one or more other Program investigators. Thus, through careful planning, and refinement of our methods, we are able to significantly reduce the number of animals used to address our scientific aims. However, it is not yet possible to replace animal experimentation as part of our efforts to understand the control of artery and vein function.